The reason they don't provide an installer DVD, is because a lot of software comes together with the laptop, as a means of publicity to you. If you reinstall from a DVD, this software/publicity is lost.
I had a same experience, waiting/searching where to find an install DVD of windows 7
(because I tend to play with my partitions :-), and I lost some.......). Then I got bored and tried to install linux (plenty of install dvd's over there)... I was a little amazed, especially about the slickness of Pinguy
! Now I have my install dvd whenever I need it...